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Ahmed, The fan mass balance probably failed because the input mass flow rate to the fan was left unconnected. Type56 does not have an output for the mass flow rate of ventilation air to my knowledge so while you can (and should) pass the flow rate of air into Type56, you can't pass it through Type56 and back to the Type112. In order to avoid that warning, you can simple connect the flow rate output of Type121 back to the fan. As far as the different results are concerned, there are a couple of things to check. First, make sure that they system is actually maintaining the set point temperatures in the zone. Type56's HEATING and COOLING types are idealized and have infinite capacity. Type92 and Type121 have limited capacity and may therefore be limited in the amount of energy that they can deliver to the zone. If they aren't delivering enough, the zone temperature will fall away from its setpoints. Second, make sure that you are looking at outputs of energy transferred to the air stream, not energy (or fuel) consumed by Type92 or Type121. Loads again are ideal and do not take into account the efficiency (COP, EER, etc) of the system that is delivering the energy. Third, Type56 is reporting sensible loads only while Type92 (if you are correctly accounting for the psychrometrics on the air stream by having a Type33 on the outlet side of Type92 in case the Type92 set point is below the air's wet bulb temperature) may be removing some latent energy as well. Kind regards, David On 12/28/2011 22:15, ahmed hamdi wrote:
-- *************************** David BRADLEY Principal Thermal Energy Systems Specialists, LLC 22 North Carroll Street - suite 370 Madison, WI 53703 USA P:+1.608.274.2577 F:+1.608.278.1475 d.bradley@tess-inc.com http://www.tess-inc.com http://www.trnsys.com |